Head injuries in sport have been described as an epidemic especially in contact sports like football, hockey and lacrosse. While catastrophic head and brain injuries are generally managed effectively, helmets have had little effect on the incidence of concussive injuries. In part this is the result of helmets used in sport, recreational pursuits and industry having primarily been designed to prevent catastrophic head injuries. Head injuries resulting from direct impacts are characterized by both linear and angular accelerations of the head during the impact. Certain types of head injuries like skull fractures and intracranial bleeds are associated with linear accelerations while injuries like concussions and subdural hematomas are thought to be more closely associated with angular accelerations. Present day foams and plastic structures used in helmets have been developed to primarily manage linear accelerations, but there are few inventions directed at managing both linear and angular accelerations.
One arrangement intended to reduce such angular accelerations is disclosed in U.S. Pat. No. 6,560,787 issued May 2003 by Mendoza which describes a layer of gel contained between two rigid bodies designed to attenuate both compressive and angular forces acting on the head. This arrangement cannot provide the reduction in angular forces sufficient to prevent head trauma.